Sorbent-based gaseous fuel storage systems such as activated carbon sorbent storage of natural gas advantageously operate at lower pressures than non-sorbent systems. For example, sorbent storage systems operate at relatively low pressures in a range of about 10 psi (0.07 MPa) to about 1000 psi (7 MPa) compared to 3,600 psi (24.821 MPa) for conventional, non-sorbent systems for internal combustion engines. While the lower pressures associated with sorbent-based systems have the potential of being more readily utilized in applications such as motor vehicles due to the fact that the systems can be less robust, bulky, complicated, and costly than high pressure systems, there have been performance drawbacks that have hindered their acceptance. In particular, getting the adsorbed gaseous fuel out of a tank and delivered to the engine for combustion in a controlled and consistent manner has been a technical challenge.
One reason for the difficulty is due to the relatively low pressures involved, which is as the amount of fuel in a tank is drawn down during operation of the engine. Specifically, the release of adsorbed gaseous fuel is typically a linear relationship with tank pressure. Thus, as the fuel is drawn from the tank, the pressure decreases, which in turn decreases the tendency of fuel to be released. This decrease in pressure has been particularly challenging to operating internal combustion engines which can often require fuel pressures that exceed that of the gaseous fuel in the tank.
Additionally, the type of sorbent and/or type of gaseous fuel can affect the fuel release. In general, the more fuel a particular fuel-sorbent combination can accommodate, the stronger the adsorbtion of the fuel. The stronger the adsorbtion, the less likely the fuel may be consistently delivered to an engine, especially as the pressure decreases. This has tended to limit the selection of sorbents, in particular, the most effective sorbents.
Still further, because the typical modern conventional engines require gaseous fuel to be pressurized for injection into the engine (e.g., up to about 200 psi), a significant amount of fuel has remained essentially unusable/inaccessible in the tank.
In view of the foregoing, a need still exists for equipment and methods for extracting a gaseous fuel from a sorbent-based storage tank in a consistent and controlled manner over a wide range of tank pressures and/or fuel levels. Further, a need still exists for the consistent and controlled delivery of gaseous fuel extracted from a sorbent-based storage tank to the fuel injection system of an internal combustion engine over a wide range of tank pressures and/or fuel levels.